(also brachypinakoid) Crystallography pertaining to either of the two planes which in the Orthorhombic system are parallel to the vertical and brachydiagonal axes respectively. [After German Brachypinakoid (1846 or earlier); compare pinacoidn.]
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1879 F. RutleyStudy of Rocks x. 97 The cleavages, which are parallel to the base and brachypinakoid.